Þingvellir National Park

Where it sits. Þingvellir lies about 40 kilometres east-northeast of Reykjavik, at the northern end of Þingvallavatn, Iceland's largest natural lake at roughly 84 square kilometres and 114 metres deep. The park floor is a lava plain, the Þingvallahraun, poured out some nine thousand years ago from the broad shield volcano Skjaldbreiður visible to the north. Two fault walls bracket it. Almannagjá forms the western edge, a face of columnar basalt running roughly seven kilometres and standing up to forty metres above the walking path. Hrafnagjá closes the eastern side about seven kilometres away. Route 36 crosses the whole thing in twenty minutes of driving, which badly flattens the scale of what is actually a sinking floor between two cliffs.

The rift underneath. Þingvellir sits inside the western volcanic zone, where the North American and Eurasian plates pull apart at roughly two centimetres a year. The popular line that a visitor can stand with one hand on each continent is a simplification: the spreading is spread across a belt of fissures tens of kilometres wide, and Almannagjá is one boundary fault of a subsiding graben rather than the seam itself. The subsidence is measurable in human time. An earthquake swarm in 1789 dropped the plain by more than half a metre in ten days, drowning part of the old assembly approach and pushing the lake shore inland. Water-filled fissures cut the plain: Silfra, Flosagjá, and Nikulásargjá, better known as Peningagjá for the coins thrown into it.

The assembly. The Alþingi first met here around 930 and returned every summer for two weeks until 1798, which makes Þingvellir the site of the oldest continuing parliamentary institution in the world. Chieftains camped in turf-walled booths whose outlines still show as low green rectangles in the grass. At Lögberg, the Law Rock, the elected lawspeaker recited a third of the legal code aloud each year from memory. It was here, around the year 1000, that Þorgeir Ljósvetningagoði ruled that Iceland would adopt Christianity while allowing private pagan practice. The site also served justice: women convicted of infanticide or adultery were drowned in the pool called Drekkingarhylur, men beheaded or hanged nearby. On 17 June 1944, in heavy rain, Iceland declared its republic at Lögberg. UNESCO inscribed the park as a cultural World Heritage Site in 2004.

On screen. Þingvellir carried a large share of Game of Thrones' Icelandic work in season four, shot in 2013. The corridor of Almannagjá, with its vertical basalt wall on one side and broken lava on the other, played the road climbing to the Bloody Gate, the fortified pass guarding the approach to the Eyrie, in the episode where Arya Stark and Sandor Clegane finally reach the Vale and learn her aunt has died. The same lava ground around the rift stands in for the mountain track in the season-four finale, where Brienne of Tarth fights the Hound. Nothing was built to last: the gate, the towers and the surrounding peaks are set dressing and digital extension. What is genuinely there is the wall, the scree and the light.

What you actually see today. From the Hakið viewpoint above P1 the whole graben opens up: lake, plain, and the two scarps. A paved path drops through Almannagjá to the plain, passing the Öxarárfoss waterfall and the flagpole at Lögberg. Þingvallakirkja, a small timber church rebuilt in 1859, stands beside the five-gabled Þingvallabær farmhouse designed by Guðjón Samúelsson for the 1930 millennium of the Alþingi; it still serves as the prime minister's summer house. Behind the church is the national burial ground holding the poets Jónas Hallgrímsson and Einar Benediktsson. Silfra, the clearest of the fissures, is fed by groundwater that seeps from Langjökull and filters through lava for decades before surfacing, giving underwater visibility of around a hundred metres in water that sits at two to four degrees all year. Snorkelling and diving there are permitted only with licensed operators and dry suits.

Getting there and timing. Route 36 from Reykjavik takes about 45 minutes and is cleared through winter. Entry to the park is free, but every car park charges a daily fee paid by number plate at a machine or online; toilets are metered separately. P1 at Hakið gives the classic descent, P2 sits below Öxarárfoss, and P5 is beside the church for a flatter approach. As the first stop on the Golden Circle, Þingvellir is busiest between ten in the morning and four in the afternoon; before nine or after six the gorge empties. The paved upper section is manageable with wheels, but the lower plain involves gravel, steps and, in winter, sheet ice that makes spikes worth carrying.